1. Field of the Invention
This invention relates to a colored, transparent film-forming composition, which is applied onto a transparent substrate made, for example, of glass, plastics or the like and used as a window of buildings or a window of vehicles, including automobiles, thereby forming a uniform, clear, transparent colored film thereon. The invention also relates to a coating method of the composition and a method for removing or separating the resultant film. More particularly, the invention relates to a film-forming composition that is able to form a fashionable film on window glass of automotive vehicles and simultaneously serves to intercept UV light, and a coating method and removal method of a film obtained from the composition.
2. Description of the Prior Art
It is a usual practice to attach, on the window of buildings or automotive vehicles, a plastic film that is formulated with a UV absorber mainly for the purpose of absorbing UV light, or a coating formulated with a UV absorber.
However, the plastic film formulated with a UV absorber has the problems of the kind of color, the technique of attaching the film, and costs. In addition, further problems are involved in that it is troublesome to cut the film in a desired form with a difficulty in attaching to a complicated portion, air cells are apt to remain upon attachment of the film, and an adhesive is left after removal of the film, so that it has not been satisfactory for everyone to make ready use of it.
Where a film-forming composition containing a UV absorber is used, it is difficult to cure an applied film at room temperature, aside from color shading absorbed to the unevenness of coating, coupled with another deficiency that film strength after curing is low.
Further, a coated film, which is time-worn, has the vital drawback that it is difficult to remove or separate the coated film, and thus, a transparent substrate is very prone to be damaged on the surface thereof.
It is accordingly an object of the invention to provide a colored, transparent film-forming composition, which is easy to handle and can yield an attractive, fashionable, transparent, colored film article and the film can be simply removed or separated from a substrate.
It is another object of the invention to provide a method for coating such a composition as mentioned above and also a removal method of a film obtained from the composition.
It is a further object of the invention to provide a colored, transparent, film-forming composition, which has a good leveling property without causing coating irregularities and can be cured at room temperature, can provide a film that is free of color shading, is high in film strength after curing, and is readily removable or separable after having been used.
It is still a further object of the invention to provide a coating method of the composition mentioned above and also a removal method of the film obtained from the composition.
According to the invention, there is provided a colored transparent film-forming composition which comprises (a) a reaction product of an epoxy group-containing alkoxysilane (a-1) and an amino group-containing alkoxysilane having active hydrogen therein (a-2), (b) an acid catalyst, (c) an alkali-soluble UV absorber, (d) at least one solvent selected from organic solvents having a boiling point of 100 to 150xc2x0 C., and (e) a dye and/or a pigment. We have found that this composition has a good property, a good room temperature-curing characteristic, a good film strength characteristic, and good film peelability.
The component (a) used in the invention is a reaction product of an epoxy group-containing alkoxysilane (a-1) and an amino group-containing alkoxysilane having active hydrogen (a-2) therein. The epoxy group-containing alkoxysilane (a-1) that is one of the constituents of the component (a) includes, for example, xcex3-glycidoxypropyltrimethoxysilane, xcex3-glycidoxypropylmethyldimethoxysilane or the like.
The amino group-containing alkoxysilane having active hydrogen (a-2), which is the other constituent of the component (a) includes, for example, xcex3-aminopropyltriethoxysilane, N-(xcex2-aminoethyl)-xcex3-aminopropyltrimethoxysilane, N-(xcex2-aminoethyl-xcex3-aminopropylmethyldimethoxysilane and the like, of which N-(xcex2-aminoethyl)-xcex3-aminopropyltrimethoxysilane of the formula, H2N(CH2)2NH(CH2)3Si(OMe)3, is preferably used.
When N-(xcex2-aminoethyl)-xcex3-aminopropyltrimethoxysilane of the formula, H2N(CH2)2NH(CH2)3Si(OMe)3, exists as a constituent of the component (a), a hard film can be formed after curing and is suitable for application to automotive window glass. If the window is opened or closed, the film is unlikely to suffer scratches therein.
For the reaction between the constituents (a-1) and (a-2), the mixing ratio by weight between the epoxy group-containing alkoxysilane (a-1) and the amino group-containing alkoxysilane having active hydrogen (a-2) should preferably be 6:4 to 9:1.
More preferably, the ratio between (a-1) and (a-2) is in the range of 7:3 to 8:2.
When the ratio by weight of the epoxy group-containing alkoxysilane is larger than 9, curing of the resultant colored, transparent film-forming composition after coating proceeds slowly, with the surface hardness of the resultant film becoming low. On the other hand, when the ratio by weight of the amino group-containing alkoxysilane having active hydrogen is larger than 4, the film of the resulting colored-transparent film-forming composition exhibits poor weatherability.
The acid catalyst used in the practice of the invention may be any one, which acts as a catalyst when the hydroxyl group-containing hydrophilic alkoxysilane compound is hydrolyzed into a more reactive silanol at room temperature and subsequently undergoes polycondensation, e.g. sulfuric acid, nitric acid, phosphoric acid, para-toluenesulfonic acid and the like. Preferably, boron trifluoride is used.
The alkali-soluble UV absorber useful in the invention may be one selected from benzophenone compounds, benzotriazole compounds, and the like provided that they are alkali-soluble. Specific examples include 2,4-dihdyroxybenzophenone, 2,2xe2x80x2, 4,4xe2x80x2-tetrahydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid and the like.
The alkali-soluble UV absorber is present in an amount of 5 wt % to 40 wt % of the colored, transparent film-forming composition. If the amount of the UV absorber is less than 5 wt %, the UV absorbing effect is lessened along with poor film separability. If the UV absorber exceeds 40 wt %, not only waterproofing and a resistance to chemicals such as an oil film cleaner and the like) are worsened, but also blooming undesirably occurs. From the standpoint of practical use, the amount preferably ranges from 15 wt % to 30 wt %.
The solvent used in the invention is made fundamentally of an alcohol solvent, a cellosolve solvent and a solvent having two or more functional groups, which, respectively, have a boiling point of 100 to 250xc2x0 C. Typical examples include isobutyl alcohol, diethylene glycol diethyl ether, diisobutyl ketone, propylene glycol monoethyl ether acetate, dipropylene glycol monomethyl ether propanol and the like.
The propylene glycol monoethyl ether acetate includes 1-ethoxy-2-propyl acetate and 2-ethoxy-1-propylacetate, and it is preferred to use a mixture of not less than 90% of 1-ethoxy-2-propylacetate and not larger than 10% of 2-ethoxy-1-propylacetate.
The solvents used in the invention have a boiling point of 100 to 250xc2x0 C. If the boiling point is lower than 100xc2x0 C., the leveling property is worsened on coating, resulting in a poor film appearance. In contrast, when the boiling point exceeds 250xc2x0 C., a coated film is unlikely to be dried.
Moreover, methyl alcohol, ethyl alcohol, methyl ethyl ketone or the like may be used in combination in order to increase solubilities of an acid catalyst and a dye.
The dyes and/or pigments used in the invention are selected from those having good weatherability for the purpose of coloring a film. Examples of the dye include direct dyes such as C.I. Direct Yellow 98, C.I. Direct Red 220, C.I. Direct Blue 77 and the like, and acid dyes such as C.I. Acid Yellow 112, C.I. Acid Red 256, C. I. Acid Blue 182 and the like. Examples of the pigment include inorganic pigments such as C.I. Pigment Yellow 157, C.I. Pigment Red 101, C.I. Pigment Blue 29 and the like, and organic pigments such as C.I. Pigment Yellow 154, C.I. Pigment Red 122, C.I. Pigment Blue 15:1 and the like. These dyes and/or pigments may be used singly or in combination. Moreover, fluorescent pigments for imparting a fluorescent color, light-storing pigments of the type wherein afterglow continues to the extent after light irradiation has stopped, iridescent pigments for imparting iridescence, temperature-indicating pigments capable of color change depending on an ambient temperature, hydrophilic pigments for imparting hydrophilicity, functional pigments for reflecting an IR ray (heat ray) and the like may be appropriately used depending on the purpose. Mention is made of a pigment made of an acrylic resin dissolving Acid Yellow 73 therein as an example of the fluorescent pigment, a pigment composed mainly of strontium aluminate as an example of the light storing pigment, a pigment composed mainly of titanium dioxide-coated mica as an example of the iridescent pigment, a pigment containing, in microcapsules, rhodamine B lactam/isocotyl galate/cetyl alcohol as an example of the temperature-indicating pigment, a pigment composed mainly of silica and titania as an example of the hydrophilic pigment, and ATO (antimony/tin oxides) ITO (indium/tin oxides) and the like fine powders as an example of the functional pigment for reflecting an IR ray (heat ray).
In the colored, transparent film-forming composition of the invention, it is preferred to further add (f) a stabilizer for an unpaired electron pair of a nitrogen atom and in order to inhibit the reaction with a UV absorber as will be caused by the unpaired electron pair of the nitrogen atom derived from an amino group-containing alkoxysilane having active hydrogen.
Various compounds may be mentioned as such a stabilizer (f), and salicylic acid, fumaric acid, crotonic acid, succinic acid, tartaric acid, para-hydroxybenzoic acid, pyrogallol, resorcinol and the like are preferably used.
These compounds used as (f) stabilizer may be used singly or in combination.
It is necessary that prior to coating onto a transparent substrate, an oil deposit or the like be removed from the surface of the transparent substrate such as of glass. Many methods of removing an oil film has been hitherto known, or which a method using a compound for oil film separation is preferred.
The colored, transparent film-forming composition of the invention can be applied by use of a brush, felt, non-woven fabric or the like.
For the coating, it is preferred to coat the composition in the direction of gravity so that an unevenness is unlikely to occur.
The colored, transparent film-forming composition of the invention is coated onto a transparent substrate, such as of glass, at room temperature, and drying to the touch is obtained within a range of from 0.5 hours to 2 hours. Further drying over 12 hours to 24 hours results in a transparent, hard, cured film of a beautiful color.
If the cured film, which is obtained by coating the colored, transparent film-forming composition of the invention onto a transparent substrate such as of glass, undergoes color degradation or is lowered in the effect of UV absorption, it is removed from the transparent substrate such as of glass and subjected to coating again.
In the practice of the invention, an alkaline detergent is used as a remover.
The alkaline agent should preferably have a pH of 9 or over. When the pH of the alkaline agent is smaller than 9, the solubility in the film is worsened. It will be noted that when the use of an alkaline agent alone does not permit infiltration into and cleaning of the film, an alkaline detergent is used wherein one or more nonionic surface active agents are formulated. Examples of the alkaline agent include anionic surface active agents, bicarbonates, sesqui-carbonates, carbonates, metasilicates, orthosilicates, phosphates, pyrophosphates, tripolyphosphates, metaborates, borates and the like in the form of sodium or potassium salts, and water-soluble amino alcohols such as triethanolamine, diethanolamine, monoethanolamine, methyldiethanolamine, ethyldiethanolamine, monoisopropanolamine, aqueous ammonia and the like. One or more of these compounds are appropriately dissolved in water and adjusted in pH to a level of 9 or over.
In addition, abrasives may be used in combination, and it is convenient to softly rub the surface with a piece of abrasive-attached sponge.
The embodiments of the invention may be summarized as follows:
(1) A colored, transparent film-forming composition comprising (a) a reaction product of an epoxy group-containing alkoxysilane (a-1) and an amino group-containing alkoxysilane having active hydrogen (a-2) therein, (b) an acid an acid catalyst, (c) an alkali-soluble UV absorber, (d) at least one solvent selected from organic solvents having a boiling point of 100 to 250xc2x0 C., and (e) a dye and/or a pigment.
(2) A colored, transparent film-forming composition as recited in (1) above, wherein the reaction product is one which is obtained by reacting the epoxy group-containing alkoxysilane (a-1) and the amino group-containing alkoxysilane having active hydrogen (a-2) at a ratio of by weight of 6:4 to 9:1.
(3) A colored, transparent film-forming composition as recited in (1) or (2) above, wherein the amino group-containing alkoxysilane having active hydrogen (a-2) consists of N-(xcex2-aminoethyl)-xcex3-aminopropyltrimethoxysilane.
(4) A colored, transparent film-forming composition as recited in any one of (1) to (3) above, wherein one or more of solvents selected from alcohol solvents, ketone solvents, ether solvents and solvents having two or more functional groups are used as an essential component.
(5) A colored, transparent film-forming composition as recited in any one of (1) to (4) above, further comprising, as (f) a stabilizer, one or more of organic compounds selected from salicylic acid, fumaric acid, crotonic acid, succinic acid, tartaric acid, parahydroxybenzoic acid, pyrogallol and resorcinol.
(6) A colored, transparent film-forming composition as recited in any one of (1) to (5) above, wherein the alkali-soluble UV absorber is used in an amount of 5 to 40 wt % of the film-forming component.
(7) A method for coating a colored, transparent film-forming composition as recited in any one of (1) to (6) above, which comprises storing (e) the dye and/or pigment component of the composition in a separate container, mixing the other components with the dye and/or pigment component immediately before the use of the composition to provide a mixed solution, impregnating the mixed solution in a coating applicator, and applying onto a pretreated transparent substrate in a direction of gravity.
(8) A method for removing a cured film comprising separating, after use, a colored film formed by curing a colored, transparent film-forming composition as recited in (1) to (6) above on a transparent substrate from the transparent substrate by use of an alkaline detergent.
The invention is described by way of examples.